The invention is based on an apparatus for the combined blow-injection of fuel and air for fuel injection systems of internal combustion engines.
Such blow-injection apparatuses are used for improved mixture preparation, by means of improved atomization of the fuel with a high relative speed between the fuel and air. Prior to entry into the combustion chamber of the engine, the fuel is intensively mixed with air. The fuel-air mixture can be blown both into the intake tube, leading to the engine cylinder, and directly into the cylinder itself.
In a blow-injection apparatus of this type (International Application WO 86/00960), two valves are disposed in line, in the axial direction of the housing, and a mixing chamber is formed between the two valves that communicates with the fuel connection. The inner valve controls the delivery of air into the mixing chamber, and the outer valve, embodied as a screen valve, controls the flow of the fuel-air mixture into the engine combustion chamber. The valve members of both valves are seated on a bar actuated by an electromagnet and are pressed onto the associated valve seats by a valve closing spring engaging the bar. Upon excitation of the magnet, both valves are opened simultaneously. As a result, air and fuel begin to flow into the mixing chamber at a ratio determined by the respective pressures and flow cross sections and flow on into the combustion chamber of the engine. As a result of the flow through the gap, the fuel is intensively mixed with the air. Metering of the quantity of fuel required per cycle is done by varying the fuel pressure in relation to the blow-injection air pressure. The metered fuel quantity is also dependent on the volume of the mixing chamber.